Vol. 62.] GLACIAL TERIOD IN" ABERDEENSHIRE, ETC. 25 



beds at Montrose, Errol, Elie, etc., where we find remains of Arctic 

 mollusca and asteroidea, apparently in the place where the animals 

 lived and died. The clay-beds at Aberdeen, as I have shown, afford 

 good evidence that the glacier of the Dee Valley retreated, before 

 the ice which came along the coast from the south gave way. Thus 

 we actually have some facts in support of the explanation which 

 I have suggested, while the absence of ordinary marine conditions 

 presented by these beds seems to render some such explanation 

 necessary. 



VIII. The last Ice-Sheet. 



Subsequent to the Red-Clay epoch, the inland ice again made a 

 great advance, and apparently for the last time. The most satis- 

 factory evidence of this in the Aberdeenshire district, is to be found 

 at the seaward end of the Dee Valley and the coast immediately to 

 the north of it. In this area there is clear proof, to one who is 

 intimately acquainted with the ground, that the Dee Glacier came 

 down to the coast with a breadth of at least 5 or 6 miles. In 

 doing so, it destroyed the lied Clay along the greater part of that 

 width, leaving some patches at the side of its track, but clearing it 

 out completely along the central portion of its route. 



The River Dee, at the lower end of its course, is bordered on the 

 south by a continuous ridge of higher ground than it is on the north. 

 The effect of this was to shunt the end of the glacier off to the 

 north-east, so that, although the river now terminates at the city of 

 Aberdeen, the central current of the ice-stream was diverted a mile 

 or two farther north, crossing the present mouth of the River Don. 

 This is well shown by the clear marks of the ice on the surface of 

 the granite at the quarries of Cairn cry and Persley, and also by the 

 fact that the Red Clay has been wiped out most completely in that 

 direction. Some patches have been left beside the present mouth 

 of the Dee, as at Torry, Ruthrieston, and the Duthie Park. 



The large mounds of coarse gravel and stones, on which much of 

 the city of Aberdeen is built, are moraines of this stream of ice 

 which came down the valley of the Dee. The Broadhill, the Castle- 

 Hill (on which the barracks are built), Ferryhill, and many other 

 eminences now covered with houses, are of this nature. In some 

 of these mounds, masses of the Red Clay are to be found which have 

 been dislodged by the ice and mixed with the moraine-gravel, 

 as, for example, on the west side of the Broadhill. Some large 

 ice-worn boulders occur in these mounds, generally near the top. 

 One of these may be seen in the quadrangle of Marischal College, 

 where it was placed a good many years ago, I believe by Prof. 

 Nicol ; but most of these big stones have been used up for building- 

 purposes long ago. 



The country around Aberdeen, before its reclamation, was so very 

 rugged and encumbered with stones, that it is difficult now to 

 realize its former appearance. Dr. James Anderson, who wrote a 

 good sketch of the district in 1791 for the then Board of Agriculture, 

 tells us that it was of the most barren nature that could anywhere 



